Bone marrow erythroid progenitor cells (CFU-E, BFU-E) were assayed in over 60 patients with a variety of B-lymphocyte neoplasms including 30 patients with chronic lymphocytic leukemia (CLL), 15 with plasma cell dyscrasias (P.C.D.), and 15 with non-Hodgkin's lymphomas (NHL). Simultaneously, marrow T-lymphocyte subsets were analyzed to determine the role of T lymphocytes in the regulation of erythropoiesis in these individuals. The results were correlated with a variety of clinical parameters including Rai stage, reticulocyte count, hemoglobin concentrations, and estimation of tumor cell mass. Compared to normals, a moderate (50% of normal) to severe (less than 25% of normal) erythroid progenitor cell production defect was observed in nearly all patients with B-cell neoplasms. In B-cell CLL, there was an inverse correlation between marrow T-suppressor cells (T gamma, OKT8+) cell numbers and erythroid progenitor cell cloning efficiency. The progenitor cell production defect correlated with Rai stage and reticulocyte count. In B-cell CLL, evidence for T-cell rather than B-cell suppression of erythroid progenitor cell growth was developed based on in vitro cell depletions and coculture studies and in vivo effects of antithymocyte globulin therapy. Preliminary results in the PCD suggest an inverse correlation between erythroid progenitor cell cloning efficiency and plasma cell mass. The erythroid progenitor cell production defect in NHL is variable and generally less severe than that observed in CLL or PCD. (MI)